1. Field of the Invention
The present invention relates generally to interposers for use in semiconductor device packages and, more specifically, to interposers that are to be assembled with semiconductor dice having bond pads arranged substantially linearly across central regions of the active surfaces thereof. In particular, the present invention relates to interposers including slots formed therethrough that are configured to facilitate the connection of bond wires to bond pads that are located proximate the edges of semiconductor dice to be assembled with the interposers. The present invention also relates to ball grid array packages including the interposers, as well as to methods for assembling the interposers with semiconductor devices and methods for forming ball grid array packages that include the interposers.
2. Background of Related Art
The dimensions of many different types of state of the art electronic devices are ever decreasing. To reduce the dimensions of electronic devices, the structures by which the microprocessors, memory devices, other semiconductor devices, and other electronic componentry of these devices are packaged and assembled with circuit boards must become more compact.
One approach to reducing the sizes of assemblies of semiconductor devices and circuit boards has been to minimize the profiles of the semiconductor devices or other electronic components upon carrier substrates (e.g., circuit boards) to which the semiconductor devices are electrically connected so as to reduce the distances the semiconductor devices protrude from the carrier substrates. Various types of packaging technologies have been developed to facilitate orientation of semiconductor devices upon carrier substrates in this manner.
One example of such a technology is the so-called xe2x80x9cflip-chip,xe2x80x9d or controlled collapse chip connection (C-4), technology. In flip-chip technology, the bond pads or contact pads of a semiconductor device are arranged in an array over a major surface of the semiconductor device. Flip-chip techniques are applicable to both bare and packaged semiconductor devices. A packaged flip-chip type semiconductor device, which typically has a xe2x80x9cball grid arrayxe2x80x9d (BGA) connection pattern, typically includes a semiconductor die and a substrate element, which is typically termed an xe2x80x9cinterposer.xe2x80x9d The interposer may be disposed over either the backside of the semiconductor die or the front (active) surface thereof.
When the interposer is positioned adjacent the backside of the semiconductor die, the bond pads of the semiconductor die are typically electrically connected by way of wire bonds or other intermediate conductive elements to corresponding contact areas on a top surface of the interposer. These contact areas communicate with corresponding bumped contact pads on the backside of the interposer. This type of flip-chip assembly is positioned adjacent to a carrier substrate with the backside of the interposer facing the carrier substrate.
If the interposer is positioned adjacent the active surface of the semiconductor die, the bond pads of the semiconductor die may be electrically connected to corresponding contact areas on an opposite, top surface of the interposer by way of intermediate conductive elements that extend through one or more holes formed in the interposer. Again, the contact areas communicate with corresponding bumped contact pads on the interposer. In this type of flip-chip semiconductor device assembly, however, the contact pads are also typically located on the top surface of the interposer. Accordingly, this type of flip-chip assembly is positioned adjacent a carrier substrate by orienting the interposer with the top surface thereof facing the carrier substrate.
In each of the foregoing types of flip-chip semiconductor devices, the contact pads of the interposer are disposed in an array that has a footprint that mirrors an arrangement of corresponding terminals formed on a carrier substrate. Each of the bond pads (on bare flip-chip semiconductor dice) or contact pads (on flip-chip packages) and its corresponding terminal may be electrically connected to one another by way of a conductive structure, such as a solder ball, that also spaces the interposer some distance away from the carrier substrate.
The space between the interposer and the carrier substrate may be left open or filled with a so-called xe2x80x9cunderfillxe2x80x9d dielectric material that provides additional electrical insulation between the semiconductor device and the carrier substrate.
In addition, each of the foregoing types of flip-chip type semiconductor devices may include an encapsulant material covering portions or substantially all of the interposer and/or the semiconductor die.
Another approach to reducing the sizes of assemblies of semiconductor devices and carrier substrates has been to reduce the amount of xe2x80x9creal estate,xe2x80x9d or surface area, upon a carrier substrate that is consumed by individual semiconductor device packages. This is typically done by reducing the dimensions of the semiconductor device packages along a plane that is parallel to a plane of the substrate upon which the semiconductor device packages are to be carried. As a result of ever-decreasing package dimensions, the so-called xe2x80x9cchip-scale packagexe2x80x9d (CSP) has been developed. The dimensions of the outer peripheries of chip-scale packages are typically substantially the same as or only slightly larger than the corresponding dimensions of the outer peripheries of the semiconductor dice that are used in chip-scale packages.
As indicated previously herein, some chip-scale packages have ball grid array connection patterns. Some ball grid array chip-scale packages include interposers that are configured to be secured over the active surfaces of semiconductor dice, with bond pads of the dice being exposed through an opening formed through the interposer. Due to the limited dimensions of chip-scale packages, the dimensions of the interposers for use therein are also constrained, as are the sizes of openings formed through the interposers. In addition, state of the art semiconductor dice typically include bond pads that are positioned very near the outer peripheries of the dice. Consequently, in order to maintain the structural integrity of chip-scale package interposers, the interposer openings may not extend a sufficient lateral distance beyond bond pads of their corresponding semiconductor devices to provide adequate clearance for the tip of a wire bonding capillary or other intermediate conductive element-forming, -positioning, or -securing apparatus to properly access the bond pads.
Accordingly, there is a need for a chip-scale package interposer that includes an opening which is configured to facilitate access to bond pads located at or near the edges of semiconductor dice by apparatus for forming, positioning, or securing intermediate conductive elements. There is also a need for a method for fabricating such interposers.
The present invention includes an interposer with a slot formed therethrough which is configured to facilitate the connection of an intermediate conductive element, such as a bond wire, to a bond pad positioned at or very near an edge of a semiconductor die to be assembled with the interposer. Semiconductor device packages that include the interposer are also within the scope of the present invention, as are methods for assembling the interposer with a semiconductor die and for forming a package that includes the interposer.
The interposer of the present invention includes a substantially planar substrate element that may be formed from any suitable material, such as resin (e.g., FR-4 resin), plastic, insulator-coated semiconductor material (e.g., silicon oxide-coated silicon), glass, ceramic, or any other suitable electrically insulative material or insulative-coated material. The interposer also includes an opening, or slot, formed therethrough. The slot is positioned to be aligned over the bond pads of a semiconductor die upon mutual positioning of the interposer and the semiconductor die. Thus, when the interposer and semiconductor die are properly oriented, the bond pads of the semiconductor die are exposed through the slot of the interposer.
A first end of the slot is configured to extend laterally beyond an outer periphery of the semiconductor die when the interposer and semiconductor die are properly oriented with respect to one another. The opposite, second end of the slot includes a laterally recessed area along only a portion thereof. The laterally recessed area of the slot is configured to receive at least a portion of a wire bonding capillary. When the interposer is properly aligned with respect to a semiconductor die, the laterally recessed area of the slot is preferably positioned adjacent a bond pad located at or very near the edge of the semiconductor die. As a result, a wire bonding capillary or other intermediate conductive element-positioning or -forming apparatus may access the bond pad located adjacent to the laterally recessed area of the slot to form an electrical connection between that bond pad and a corresponding contact area on a surface of the interposer.
A semiconductor device package incorporating teachings of the present invention includes a semiconductor die, an interposer positioned over an active surface of the semiconductor die, wire bonds connecting bond pads of the semiconductor die to corresponding contact areas of the interposer, and a quantity of encapsulant material at least partially filling the slot formed through the interposer and at least partially covering the active surface of the semiconductor die. The encapsulant material may also extend at least partially onto the surface of the interposer and above the surface of the interposer to substantially encapsulate the bond wires that connect bond pads of the semiconductor die to corresponding contact areas of the interposer.
A method for fabricating the interposer includes providing a substantially planar substrate and forming a slot therethrough at an appropriate location. In forming the slot, a laterally recessed area is formed at an end of the slot. One example of the manner in which a slot with a laterally recessed area at an end thereof may be formed includes using a first drill bit to form a first, small hole through the substantially planar substrate element at a location where the laterally recessed area of the slot is to be positioned. The remainder of the slot is formed by using a second, larger diameter drill bit (e.g., a router bit) to form a second, larger hole proximate the location of the first, small hole and by moving the second drill bit longitudinally to elongate the second hole. Alternatively, a first drill bit may be used to form a narrow slot, then a second, larger diameter drill bit may be used to widen the slot along the length thereof except in the location where the laterally recessed area is to be located. In this case, the laterally recessed area is the remaining, narrow portion of the slot formed by the first drill bit. Thus, the first, narrower slot serves as a reference by which the second, larger drill bit that is used to form the majority of the slot is positioned.
While the foregoing exemplary methods may be used to form a slot with a laterally recessed area at a portion of an end thereof on any type of substrate element, including, without limitation, a resin, a plastic, dielectric-coated silicon (e.g., silicon oxide-coated silicon), glass, ceramic and other suitable insulative or insulator-coated substrate elements, slots having a laterally recessed area formed in only a portion of a periphery (e.g., at an end) thereof may be formed by other suitable techniques. For example, if the substrate element of the interposer is formed from silicon or another etchable material, such as glass or ceramic, known patterning processes, such as the use of known masks and etchants, which are typically used in semiconductor device fabrication processes may be employed to define a slot in the substrate element, as well as a laterally recessed area in a peripheral edge of the slot.
Other features of the interposer, such as contact areas, conductive traces, conductive vias, and terminals, may be fabricated by known circuit board or semiconductor device fabrication processes.
Other features and advantages of the present invention will become apparent to those of ordinary skill in the art through consideration of the ensuing description, the accompanying drawings, and the appended claims.